Re: Bastnaesite
Generally speaking, the term "bastnaesite" denotes a group of minerals that are chiefly comprised of fluorocarbonates of certain rare earth elements. However, the nomenclature used to describe these minerals is often rather loosely employed. For example, since the chief components of bastnaesite are rare earths, these minerals are sometimes referred to as rare earth oxides. They also are commonly referred to as "lanthanides." This term is obviously a corruption of the word lanthanum, which is the first member (or lowest atomic number member) of the lanthanide group of the Periodic Table. Those familiar with this art also will appreciate that the chemical symbol for lanthanum ("Ln") is commonly used to denote all of the lanthanides when they are considered as a group.
It also is common practice to refer to the various oxides of the lanthanides as LnO and to their oxyfluorides as LnOF. Given all of these considerations, it is quite common to designate the chemical makeup of bastnaesites, in general, by the formula: (Ce,La)OF, even though this mineral contains many other elements. For example, most bastnaesite minerals contain from about 65% to about 80% by weight of assorted rare earth elements (calculated as rare earth oxides). Their primary components are lanthanum and cerium, but they usually contain smaller proportions of various other rare earth elements such as praseodymium, neodymium, samarium, europium, and gadolinium. For example, chemical analysis of a typical bastnaesite mineral might show proportions of individual rare earth elements (calculated as oxides) to total rare earth elements (also calculated as oxides) within the general ranges: 45 to 55 wt. % CeO.sub.2, 29 to 35 wt. % La.sub.2 O.sub.3, 11 to 15 wt. % Nd.sub.2 O.sub.3, 2.5 to 5.5 wt. % Pr.sub.2 O.sub.3, 0.3 to 0.7 wt. % Sm.sub.2 O.sub.3, 0.1 to 0.3 wt. % Gd.sub.2 O.sub.3, 0.05 to 0.15 wt. % Eu.sub.2 O.sub.3, and 0.05 to 0.35 wt. % of other rare earth elements.
Next, note that bastnaesite is a somewhat chemically reactive mineral. Consequently, it can be modified by relatively moderate chemical and/or physical treatment processes such as steaming, calcining, and acid leaching. By way of example of such a modification, bastnaesite ore is sometimes leached with strong acids to withdraw some or all of its strontium and barium content with which it is associated. Hence, for the purposes of this patent disclosure, the terms "bastnaesite," "treated bastnaesite," "bastnaesite mineral(s)" should be taken to include not only those raw mineral forms of bastnaesite found in nature, but also a wide variety of physically or chemically treated forms of such minerals.